Biological tissue heart valves have evolved into several specialized designs to satisfy the on-going need of patients for a valve that will be free from structural failures and will last for the life of the adult. The primary focus of new designs for such valves has been to significantly increase the mechanical as well as the biological durability of the valve. In addition to the foregoing, these valves should be easy for surgeons to implant without any distortion and with consistent results, and the sewing ring design for an aortic valve should be compliant to accommodate both the calcific annulus as well as the annulus of a bicuspid valve.
Overall, tissue valves are still being sought that meet the following objectives: (1) low stresses at the coaptation surface of the leaflets in the closed position; (2) synchronous and symmetrical leaflet motion; (3) wrinkle-free leaflets at all phases of leaflet motion; (4) even alignment of the free margins of the tissue; and (5) hemodynamic efficiency from a trefoil stent design for the aortic position.